Manufacture of electrical rectifiers



April 3, 1929. o; a. ACKERLY 1,709,830

MANUFACTURE OF ELECTRICAL REGTIFIERS Filed Aug. 26, 1926 A C A CA I I l I I A/ v y- A p V D E lly-3 INVENTOR I QIR'W Patented Apr. 23, 1929.

UNITED STATES PATENT OFFICE.

DONALD G. ACKERLY, F WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO THE UNION SWITCH 80 SIGNAL COMPANY, OF SWISSVALE, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

- MANUFACTURE OF ELECTRICAL BECTIFIERS.

Application filed August 26, 1926. Serial No. 131,700.

My invention relates to the manufacture of electrical rectifiers, and more particularly to the manufacture of elements for rectifiers of the type disclosed and claimed in an applieation for Letters Patent of the United States, filed by Lars O. Grondahl, on J anuary 7, 1925, Serial No. 1,111, for uni-directional current carrying devices.

I will describe two processes of manufac- Lo ture embodying my invention, and will then point out the novel features thereof in claims.

In the accompanying drawing, Figs. 1 and 2 are views showing, in end elevation .5 and vertical cross-section, respectively, a number of blanks ready to be prepared as a rectifier element in accordance with my invention. Fig. 3 is a View showing in vertical cross-section one form of rectifier element :0 as it would appear at one stage in the process of manufacture embodying my invention. Fig. 4 is a view similar to Fig. 3 showing the completed rectifier element. are views showing in end elevation and vertical cross-section, respectively, a pair of blanks ready to be prepared in accordance with a modified form of process also embodying my invention.

Similar reference characters refer to o similar parts in each of the several .views.

Rectifier elements of the type described are usually prepared by forming upon a metallic blank, such as copper or iron, a compound of the metal such as the oxide or ,5 the iodide. If the rectifier element is pre-- pared by oxidizing acopper blank, it is necessary to remove a portion of the oxide coating from the copper blank to provide terminals for connecting the elementwith an .0 external circuit. One process for removing the oxide coating is described and claimed in an application for Letters Patent of the United States, Serial No. 131.620, filed on even date herewith, by Paul H. Geiger and .5 WVarren S. Brown, for manufacture of electrical rectifiers. Then the oxide coating is removed by the process disclosed by that application, it has been found of advantage to form the coating of non-uniform thickness. The purpose of the present invention is the provision of a process of manufacturein which the oxidation of a portion of the surface of the copper blank is retarded.

Referring now to Figs. 1 and 2, the cop- Figs. 5 and 6 of blanks.

per blanks A which as here shown are of fiat circular form, are each provided with a centrally located aperture A The blanks are assembled in pairs upon a horizontally extending support B. In the form here shown the support B is a bar which passes through the apertures A .in blanks A and is provided on its upper side with a plurality of notches B each having downwardly converging side walls 1 and 2 spaced apart sufficiently to accommodate between them, two of the blanks A. A pair of the blanks is placed in each of the notches B and the space between the/blanks of each such pair is filled with a mass C of deoxidizing agent. I have discovered that carbon is particularly suitable for this purpose. Due to'the cone verging side walls of each of the notches B the weight of the blanks A forces the blanks closely together.

Any appropriate number .of the blanks are assembled in the manner just described upon the support B and are then subjected to an oxidizing process such, for example, as

theapplication of heat. During this process that face of the blank which was covered with the de-oxidizing agent during the oxidation process. The oxidized unit is then treated to remove the black oxide from the entire surface of the blank. The oxide may be removed from the blank in the manner disclosed in the Geiger and Brown application referred to hereinbefore, or in any other suitable manner so that the rectifier unit in its completed form appears as shown in In a modified form of process of manufacture embodying my invention the nonuniform oxide .coating may be formed upon the blanks by excluding oxygen from a portion of the surface of the blanks during the oxidation process. One method of accomplishing this result is to fit an annular rim G around the peripheries of each pair of blanks A, as best shown in Figs. 5 and 6. The rim can be made of thin co per or of a non-oxidizing alloy and fits tig itly about the blanks so that oxygen is excluded from the adjacent surfaces of each pair of blanks. Of course these adjacent surfaces are supplied with a small amount of oxygen which enters the space between the blanks through the apertures A but when the blanks are placed upon the support B, the wedging effect of notches B has a tendency to urge the edges of the blanks adjacent their aligned apertures A into contact and when the blanks are oxidized with the rim G in place as shown in Figs. 5 and 6, substantially no oxide is formed upon the ad ac-ent surfaces of each pair of units. After the elements have been oxidized with the rim G in place, the rim is removed, the blanks are separated and a portion of the oxide is removed to complete the rectifier elements as explained hereinbefore. 2

Although I have herein shown and described only two processes for manufactur-' so that an oxide coating of noi'i-unifornr thicknessis formed directly on the blank.

4. A support for holding flat apertured blanks during oxidation. comprising a bar entering the apertures in said blanks, and having notches in one side of the bar each provided with converging side walls and each notch receiving two blanks whereby the blanks are urged toward one another by the converging walls of the notch.

5. In a process of preparing a rectifier element by oxidation of a metallic blank, the step of retarding the oxidation of the blank over a portion of its surface with a deoxidizing material applied to that portion of the surface.

6. The process of preparing a rectifier element from a copper blank which consists in applying carbon to part but not all of the surface of the blank, and heating the blank.

inthe presence .of oxygen whereby oxides are formed on the exposed surface of the blank but not on the surface covered by car bon.

In testimony whereof I aflix my signature.

DONALD G. ACKERLY. 

